James Kirkup is The Telegraph's Executive Editor (Politics). He was previously the Telegraph's Political Editor and has worked at Westminster since 2001.

PMQs: Ed Balls, the 'muttering idiot', gets under David Cameron's skin again

Conservative MPs loved it, and their support was only boosted by the order from John Bercow to withdraw the remark. But David Cameron's description of Ed Balls as "the muttering idiot opposite" may not have been the PM's best moment.

Mr Balls takes great pleasure in heckling his Oxford contemporary, feeling that the PM's temperament is a bit suspect. This isn't the first time he's achieved the effect he seeks, a moment of prime ministerial anger.

The politics of Mr Cameron's anger remain slightly unclear to me. There's an argument to be made that showing some fire is a good thing: voters may prefer a passionate leader to a bloodless one. And Conservative supporters will probably like their leader taking the fight to the likes of Mr Balls.

Still, there's a very fine balance to be struck. Too much passion and you start to look a bit undisciplined; most voters probably want a leader who is in control of his feelings, not hostage to them. I don't think the idea of David Cameron as red-faced ranter has much resonance outside Westminster at the moment, but the idea could eventually catch on, damagingly.

(As an aside, I wonder if Mr Cameron's enemies are going to have to decide which caricature of him they want to offer: angry Flashman or idle chillaxer? Or can he painted as both? A question for another day, perhaps.)

One thing does seem quite clear though: today's flash of temper will only encourage Mr Balls and his Labour friends to go on needling Mr Cameron. We will see more such moments in future.